U.S. patent application number 15/239062 was filed with the patent office on 2018-02-22 for temperature controller of semiconductor wafer.
The applicant listed for this patent is KELK Ltd.. Invention is credited to Kazuhiro Mimura.
Application Number | 20180053668 15/239062 |
Document ID | / |
Family ID | 61192063 |
Filed Date | 2018-02-22 |
United States Patent
Application |
20180053668 |
Kind Code |
A1 |
Mimura; Kazuhiro |
February 22, 2018 |
Temperature Controller of Semiconductor Wafer
Abstract
A temperature controller for a semiconductor wafer is configured
to perform a temperature control on a plurality of temperature
adjusters including a reference temperature adjuster to perform a
temperature adjustment of the semiconductor wafer, in which a
manipulated variable calculator to give a manipulated variable to a
master loop and a slave loop includes a master-slave switching unit
configured to switch between the master loop and the slave loop and
a master-slave cancellation unit configured to cancel a setting of
the master loop and the slave loop when a temperature setpoint of
the slave loop is set to have a temperature gradient against a
temperature setpoint of the master loop.
Inventors: |
Mimura; Kazuhiro;
(Hiratsuka-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KELK Ltd. |
Hiratsuka-shi |
|
JP |
|
|
Family ID: |
61192063 |
Appl. No.: |
15/239062 |
Filed: |
August 17, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G05B 2219/2237 20130101;
G05D 23/22 20130101; G05B 19/042 20130101; H01L 21/67109 20130101;
H01L 21/67248 20130101; G05B 2219/45031 20130101; G05D 23/1934
20130101 |
International
Class: |
H01L 21/67 20060101
H01L021/67; G05B 19/042 20060101 G05B019/042; G05D 23/19 20060101
G05D023/19; G06F 17/16 20060101 G06F017/16 |
Claims
1. A temperature controller for a semiconductor wafer, the
temperature controller configured to perform a temperature control
of a plurality of temperature adjusters comprising a reference
temperature adjuster to perform a temperature adjustment of the
semiconductor wafer, the temperature controller comprising: a
master loop configured to perform a temperature control of the
reference temperature adjuster; a slave loop configured to perform
a temperature control of the temperature adjuster(s) other than the
reference temperature adjuster to follow the master loop; a master
temperature detector configured to detect a temperature of the
semiconductor wafer subjected to the temperature adjustment by the
reference temperature adjuster of the master loop; a slave
temperature detector configured to detect the temperature of the
semiconductor wafer subjected to the temperature adjustment by the
temperature adjuster(s) of the slave loop; and a manipulated
variable calculator configured to calculate a manipulated variable
to be given to the reference temperature adjuster of the master
loop and a manipulated variable to be given to the temperature
adjuster(s) of the slave loop, based on the temperature detected by
the master temperature detector and the temperature detected by the
slave temperature detector, the manipulated variable calculator
comprising: a master-slave switching unit configured to switch
between the master loop and the slave loop according to setting
conditions of a temperature setpoint of the master loop and a
temperature setpoint of the slave loop before and after being
changed; and a master-slave cancellation unit configured to cancel
a setting of the master loop and the slave loop when the
temperature setpoint of the slave loop is set by adding a
temperature gradient to the temperature setpoint of the master
loop.
2. The temperature controller for the semiconductor wafer according
to claim 1, wherein the master-slave switching unit is configured
to switch the master loop to a loop having a lowest temperature
setpoint in a heating control and to a loop having a highest
temperature setpoint in a cooling control.
3. The temperature controller for the semiconductor wafer according
to claim 1, wherein the slave loop comprises two or more slave
loops, and the temperature gradient in three or more levels is set
between the master loop and the two slave loops, and the
master-slave cancellation unit cancels the setting of the master
loop when the temperature gradient set in the three or more levels
is inverted during the temperature control.
4. The temperature controller for the semiconductor wafer according
to claim 2, wherein the slave loop comprises two or more slave
loops, and the temperature gradient in three or more levels is set
between the master loop and the two slave loops, and the
master-slave cancellation unit cancels the setting of the master
loop when the temperature gradient set in the three or more levels
is inverted during the temperature control.
Description
TECHNICAL FIELD
[0001] The present invention relates to a temperature control
device for a semiconductor wafer, the temperature control device
being configured to perform a temperature control of a plurality of
temperature adjusters to perform a temperature adjustment of the
semiconductor wafer.
BACKGROUND ART
[0002] A process for treating a semiconductor wafer such as a
silicon wafer includes controlling an in-plane temperature
distribution of the silicon wafer as desired while controlling the
temperature of the silicon wafer to a temperature setpoint.
[0003] For this purpose, there has been known a method of
controlling the temperature of the semiconductor wafer
simultaneously using a plurality of temperature adjusters through
independent control loops respectively provided to the temperature
adjusters.
[0004] Regarding the above temperature control for a semiconductor
wafer, it is necessary that control variables should have a certain
error from a reference control variable until the temperature
reaches a setpoint and that the temperature should be maintained at
the setpoint irrespective of any disturbance. In connection with
the above, a master-slave control method is typically known (see,
for instance, Patent Literature 1: JP-A-7-200076).
[0005] In the master-slave control method, one of a plurality of
control loops is controlled as a master, and an error between a
control variable (a setpoint) of the master loop and a control
variable of the rest (a slave loop(s)) of the control loops is
calculated and controlled so that the slave loop(s) follows the
behavior of the master loop.
[0006] Usually, the control loop having the slowest response speed
is defined as the master loop and the rest of the control loops is
defined as the slave loop following the master loop.
[0007] When the master-slave control method is applied to a
plate-shaped temperature adjustment device for a semiconductor
which includes a plurality of heating and cooling zones,
temperatures of all the zones are made uniform, or alternatively,
the plate is made to have temperature gradient with different
temperature setpoints for the zones, depending on usage. For
instance, when the plate is placed in a chamber, the semiconductor
wafer is liable to be affected by heat of walls of the chamber, so
that a periphery of the plate may be easily heated than the center
thereof.
[0008] In such a case, a temperature setpoint of a central zone of
the plate needs to be set high while a temperature setpoint of a
peripheral zone of the plate needs to be set low. For this setting,
an offset temperature, which is suitable for a temperature adjuster
in the slave loop relative to a temperature setpoint of a
temperature adjuster in the master loop, is set for adjustment.
[0009] However, although described in more detail later, in the
master-slave control method, heating and cooling in the plate with
a temperature gradient cause problems below.
[0010] Specifically, when a control loop having the highest
temperature setpoint is set as the master loop in the heating, the
slave loop is set to have a temperature setpoint that includes a
certain offset against the temperature setpoint of the master loop.
Accordingly, when the master loop starts to be executed for
heating, the slave loop temporarily starts being executed for
cooling against the master loop so as to provide a certain
offset.
[0011] Moreover, for instance, when the temperatures of three zones
are stabilized in a steady state at the respective temperature
setpoints (SV1, SV2, SV3)=(10.degree. C., 20.degree. C., 30.degree.
C.) and, subsequently, the temperature setpoints are inverted to
(SV1, SV2, SV3)=(30.degree. C., 20.degree. C., 10.degree. C.), the
temperature in the middle zone deviates from the temperature
setpoint SV2 at the moment of switching between the temperature
setpoints although the temperature setpoint SV2 is supposed to be
unchanged. Such an error requires more time for stabilizing the
temperature to the temperature setpoint, which adversely affects
throughput.
SUMMARY OF THE INVENTION
[0012] An object of the invention is to provide a temperature
control device for a semiconductor wafer, in which the temperature
control device employs a master-slave control method and is capable
of improving throughput.
[0013] In a first aspect of the invention, a temperature controller
for a semiconductor wafer is configured to perform a temperature
control of a plurality of temperature adjusters including a
reference temperature adjuster to perform a temperature adjustment
of the semiconductor wafer, and includes: a master loop configured
to perform a temperature control of the reference temperature
adjuster; a slave loop configured to perform a temperature control
of the temperature adjuster(s) other than the reference temperature
adjuster to follow the master loop; a master temperature detector
configured to detect a temperature of the semiconductor wafer
subjected to the temperature adjustment by the reference
temperature adjuster of the master loop; a slave temperature
detector configured to detect the temperature of the semiconductor
wafer subjected to the temperature adjustment by the temperature
adjuster(s) of the slave loop; and a manipulated variable
calculator configured to calculate a manipulated variable to be
given to the reference temperature adjuster of the master loop and
a manipulated variable to be given to the temperature adjuster(s)
of the slave loop, based on the temperature detected by the master
temperature detector and the temperature detected by the slave
temperature detector, in which the manipulated variable calculator
includes: a master-slave switching unit configured to switch
between the master loop and the slave loop according to setting
conditions of a temperature setpoint of the master loop and a
temperature setpoint of the slave loop before and after being
changed; and a master-slave cancellation unit configured to cancel
a setting of the master loop and the slave loop.
[0014] In a second aspect of the invention, the master-slave
switching unit is configured to switch the master loop to a loop
having a lowest temperature setpoint in a heating control and to a
loop having a highest temperature setpoint in a cooling
control.
[0015] In a third aspect of the invention, the slave loop comprises
two or more slave loops, and the temperature gradient in three or
more levels is set between the master loop and the two slave loops,
and the master-slave cancellation unit cancels the setting of the
master loop when the temperature gradient set in the three or more
levels is inverted during the temperature control.
[0016] According to the first aspect of the invention, since the
master-slave switching unit and the master-slave cancellation unit
are provided, the master-slave relationship can be switched or the
setting of the master-slave relationship can be cancelled by
providing a constant temperature or a temperature gradient among
the master loop and slave loops, it is preventable that the slave
loops demonstrate a response in a temperature-lowering direction as
the temperature of the temperature adjuster of the master loop
starts increasing at the start of the temperature control, or the
slave loops demonstrate a response in a temperature-increasing
direction as the temperature of the temperature adjuster of the
master loop starts decreasing, and throughput of the temperature
control device is improvable.
[0017] According to the second aspect of the invention, since the
master-slave switching unit is provided, since the loop having the
lowest temperature setpoint is switched to the master loop in the
heating control and the loop having a highest temperature setpoint
is switched to the master loop in the cooling control, the slave
loop(s) does not demonstrate a setpoint response in an inverse
direction at the start of the control, so that the throughput of
the temperature control device is reliably improvable.
[0018] According to the third aspect of the invention, since the
master-slave cancellation unit cancels the master-slave
relationship, even when the temperature gradient set in three or
more levels is inverted, a deviation is unexpected in the setpoint
response of the loop having an intermediate temperature setpoint
set between the highest temperature setpoint and the lowest
temperature setpoint.
BRIEF DESCRIPTION OF DRAWING(S)
[0019] FIG. 1 is a block diagram showing a temperature adjustment
device according to an exemplary embodiment of the invention.
[0020] FIG. 2A is a cross-sectional view showing an arrangement of
a temperature adjuster and a temperature sensor in the exemplary
embodiment.
[0021] FIG. 2B is a plan view showing the arrangement of the
temperature adjuster and the temperature sensor in the exemplary
embodiment.
[0022] FIG. 3 is a block diagram showing a configuration of a
controller that controls the temperature adjustment device
according to the first exemplary embodiment.
[0023] FIG. 4A is a schematic diagram for explaining matrix
transformation in a manipulated variable converter in the exemplary
embodiment.
[0024] FIG. 4B is another schematic diagram for explaining matrix
transformation in a manipulated variable converter in the exemplary
embodiment.
[0025] FIG. 5 is a flow chart for explaining the effects of the
first exemplary embodiment.
[0026] FIG. 6 is a schematic diagram showing a control system used
for simulation for checking effects in the exemplary
embodiment.
[0027] FIG. 7 is a plan view showing the control system used for
simulation for checking effects in the exemplary embodiment.
[0028] FIG. 8 is a block diagram showing a configuration of a
typical master-slave control.
[0029] FIG. 9A is a graph showing results of simulation with
respect to typical problems.
[0030] FIG. 9B is another graph showing results of simulation with
respect to typical problems.
[0031] FIG. 10 is still another graph showing results of simulation
with respect to typical problems.
[0032] FIG. 11A is a graph showing simulation results in the
exemplary embodiment.
[0033] FIG. 11B is another graph showing simulation results in the
exemplary embodiment.
[0034] FIG. 12 is still another graph showing simulation results in
the exemplary embodiment.
DESCRIPTION OF EMBODIMENT(S)
[0035] Exemplary embodiment(s) of the invention will be described
below with reference to the attached drawings.
1. Structure of Temperature Adjustment Device 1
[0036] FIG. 1 shows a temperature adjustment device 1 according to
a first exemplary embodiment of the invention. The temperature
adjustment device 1 controls a temperature of a silicon wafer W
placed on a plate-shaped stage 2 to a temperature setpoint to
control an in-plane temperature distribution of the silicon wafer
W. The temperature adjustment device 1 is used, for instance, in a
dry process.
[0037] The temperature adjustment device 1 includes the
plate-shaped stage 2 and a temperature adjuster 3. The temperature
adjuster 3 is preferably provided in a form of a chiller device or
a thermoelectric element when used for heating and cooling control.
When used only for heating control, the temperature adjuster 3 can
be in a form of a heater.
[0038] The stage 2 is disposed in a vacuum chamber 4. The silicon
wafer W is placed on the stage 2. The silicon wafer W is
electrostatically held on the stage 2. It should be noted that
helium gas may be delivered between the stage 2 and the silicon
wafer W to enhance efficiency in heat transfer between the stage 2
and the silicon wafer W.
[0039] In the dry process, the vacuum chamber 4 is air-purged to be
kept at a predetermined low pressure state.
[0040] In the stage 2, a plurality of temperature adjusters 3 are
disposed as shown in FIGS. 2A and 2B so as to adjust the in-plane
temperature distribution of the silicon wafer W placed on the stage
2.
[0041] FIG. 2A is a cross-sectional view of the stage 2. The
temperature adjusters 3 are disposed on a base plate 7. A plate 5
is placed on the temperature adjusters 3. A temperature sensor 6 (a
temperature detector) is disposed in the plate 5.
[0042] FIG. 2B is a plan view of the stage 2, showing that the
stage 2 is divided into three concentric zones 2A, 2B, 2C, in each
of which the temperature adjusters 3 are disposed. The temperature
sensors 6 in the plate 5 are disposed at positions corresponding to
the temperature adjusters 3.
[0043] The zones 2A, 2B and 2C of the stage 2 can be independently
heated by electrifying the temperature adjusters 3. Accordingly, by
adjusting electrification to each of the temperature adjusters 3 to
control the temperature adjusters 3, the in-plane temperature
distribution of the silicon wafer W on the stage 2 is adjustable.
The temperature adjusters 3 in each of the zones 2A, 2B and 2C are
controlled by a controller 24.
2. Structure of Controller 24
[0044] The controller 24 controls the temperature adjusters 3,
which include master temperature adjusters 3M and slave temperature
adjusters 3S, based on temperatures detected by the temperature
sensor 6 as described above, and has a functional configuration as
shown in a block diagram of FIG. 3.
[0045] The controller 24 includes: a master loop ML for controlling
temperature adjusters 3M configured to heat the zone 2A shown in
FIGS. 2A and 2B; a slave loop SL for controlling temperature
adjusters 3S configured to heat the zones 2B and 2C; a master
temperature sensor 6M configured to detect the temperature of each
of the temperature adjusters 3M; a slave temperature sensor 6S
configured to detect the temperature of each of the temperature
adjusters 3S; and a manipulated variable calculator 30 that
calculates a manipulated variable for each of the master loop ML
and the slave loop SL. It should be noted that the slave loop SL
includes two loops for the zones 2B, 2C that similarly follow the
master loop ML, and thus only one of the loops is shown in FIG.
3.
[0046] In a master-slave control system, a control variable for a
slave side follows a control variable for a master side to control
the temperature distribution. Accordingly, when the temperatures of
the zones 2A, 2B and 2C are uniformly controlled relative to the
same temperature setpoint, since the maximum response speed of the
control system is usually limited by a loop with the slowest
response speed, the loop with the slowest response speed should be
defined as the master loop ML.
[0047] The manipulated variable calculator 30 applies manipulated
variables MVm, MVs based on a master control setpoint SVm and a
slave control setpoint SVs to the temperature adjusters 3M, 3S,
respectively.
[0048] The manipulated variable calculator 30 includes a master
error calculator 31M, a slave error calculator 31S, a master
control processor 32M, a slave control processor 32S, a manipulated
variable converter 33, a master manipulated variable regulator 34M,
a slave manipulated variable regulator 34S, a setpoint setting
section 35 for the zone 2B, a setpoint setting section 36 for the
zone 2A, and a supervisor 37 serving as a master-slave cancellation
unit, a master-slave switching unit and an internal temperature
setpoint calculator. Herein, the internal temperature setpoint
refers to a temperature setpoint for master-slave control which is
calculated by the supervisor 37 using the temperature setpoints of
the zones set by the setpoint setting sections. When the
master-slave relationship is cancelled, the temperature setpoint is
equal to the internal temperature setpoint.
[0049] The master error calculator 31M and the slave error
calculator 31S respectively calculate a master loop error em and a
slave loop error es with use of the internal temperature setpoint
calculated by the supervisor 37 and temperature sensor detection
values PVm and PVs of the zones.
[0050] The master control processor 32M, an example of which is a
PID controller, outputs a calculation result Um to the manipulated
variable converter 33.
[0051] The slave control processor 32S similarly outputs a
calculation result Us to the manipulated variable converter 33.
[0052] The manipulated variable converter 33 is configured to
convert the inputted calculation result Um from the master control
processor 32M and calculation result Us from the slave control
processor 32S into manipulated variables so that interaction
between the master loop ML and the slave loop SL is reduced. The
two inputs Um, Us are converted into the two outputs Vm, Vs using a
transformation matrix H and the thus-obtained master manipulated
variables Vm and slave manipulated variable Vs are outputted. The
transformation matrix H is obtained from, for instance, a
steady-state gain matrix Gp=P(0) and a master-slave manipulated
variable transformation matrix Gm, given that a target to be
controlled is represented by a transfer function matrix P(s). The
transformation matrix H for obtaining the manipulated variables is
represented by the following formula (1), given that the transfer
function matrix P(s) has two rows and two columns.
[ V m V s ] = H [ U m U s ] = [ h 11 h 12 h 21 h 22 ] [ U m U s ] H
= ( Gm Gp ) - 1 Gp = P ( 0 ) ( 1 ) ##EQU00001##
[0053] The master manipulated variable regulator 34M regulates the
manipulated variable so that the output of the temperature
adjusters 3M falls within a range from the minimum output to the
maximum output thereof When determining that the manipulated
variable reaches a saturation level, the master manipulated
variable regulator 34M outputs a corresponding determination signal
awm to the master control processor 32M. The output of the master
manipulated variable regulator 34M is outputted as the manipulated
variable MVm to the temperature adjusters 3M.
[0054] Similarly, the slave manipulated variable regulator 34S
regulates the manipulated variable so that the output of the
temperature adjusters 3S falls within a range from the minimum
output to the maximum output thereof When determining that the
manipulated variable reaches a saturation level, the slave
manipulated variable regulator 34S outputs a corresponding
determination signal aws to the slave control processor 32S. The
output of the slave manipulated variable regulator 34S is outputted
as the manipulated variable MVs to the temperature adjusters 3S.
The determination signals awm, aws function as anti-windup
activation signals in the master control processor 32M and the
slave control processor 32S, respectively.
[0055] Based on information of the current temperature setpoint,
the changed temperature setpoint, and the current temperatures of
the zones, the supervisor 37 is configured: to output the internal
temperature setpoint, which has been changed according to a
changing pattern, to the error calculators 31M, 31S of the zones;
to determine and output a command for switching between the master
loop and the slave loop and cancelling the relationship between the
master loop and the slave loop; and to determine and output a
command for switching the transformation matrix in the manipulated
variable converter 33.
[0056] As shown in a flowchart described below, the supervisor 37
finishes switching between the master loop and the slave loop and
cancelling the relationship between the master loop and the slave
loop, and switching the transformation matrix, before outputting
the internal temperature setpoint to the error calculators 31M,
31S. The control processors 32M, 32S, which perform a typical
output calculation based on the errors calculated by the error
calculators 31M, 31S, add a processing of bumplessly switching
between the master loop and the slave loop and cancelling the
relationship between the master loop and the slave loop according
to the respective commands.
[0057] The supervisor 37 also switches the transformation matrix in
the manipulated variable converter 33. The transformation matrix is
switched as follows. The transformation matrix indicates a product
of a transformation matrix S of states and a decoupling matrix D
for reducing interaction of a plant.
H=S.times.D
[0058] In other words, the supervisor 37 switches the
transformation matrix S. A switching of the transformation matrix S
is performed below, for instance, for three zones.
[0059] When a zone 1 is a master, the switching of the
transformation matrix S is equivalent to adding an output of the
zone 1 to an output of each of the other slaves.
S 1 = [ 1 0 0 1 1 0 1 0 1 ] ( 2 ) ##EQU00002##
[0060] When a zone 3 is a master, the switching of the
transformation matrix S is equivalent to adding an output of the
zone 3 to an output of each of the other slaves.
S 3 = [ 1 0 1 0 1 1 0 0 1 ] ( 3 ) ##EQU00003##
[0061] When the master-slave relationship is cancelled, the outputs
of the zones are each independently processed.
S 0 = [ 1 0 0 0 1 0 0 0 1 ] ( 4 ) ##EQU00004##
[0062] The manipulated variable converter 33 switches among these
three matrixes in response to the command from the supervisor
37.
[0063] Next, a bumpless switching will be described.
[0064] In the manipulated variable converter 33 of a three-input
three-output system, when the zone 1 is defined as the master, the
zones 2 and 3 are defined as the slave output, and outputs of the
respective controllers in a steady state before the switching are
respectively defined as U1, U2 and U3 as shown in FIG. 4A, the
output of the manipulated variable converter 33 is subjected to a
state conversion in the transformation matrix H and is subsequently
decoupled by the decoupling matrix D. After the state conversion of
the outputs U1, U2 and U3 of the manipulated variable converter 33
before the switching, the outputs of the respective zones are as
follows.
Zone 1: U1
Zone 2: U2+U1 (5)
Zone 3: U3+U1
[0065] When the master loop is switched from the zone 1 to the zone
3 and the outputs at which the manipulated variable converter 33
can keep the steady state even after the switching are defined as
V1, V2 and V3 as shown in FIG. 4B, the outputs of the zones after
the state conversion are shown below.
Zone 1: V1+V3
Zone 2: V2+V3 (6)
Zone 3: V3
[0066] If (5)=(6) before and after the switching, the output is
unchanged, so that the zone 3 is shown as follows:
V3=U3+U1.
[0067] Since the zone 1 is shown as follows based on V1+V3=U1:
V1=U1-V3=U1-(U3+U1)=-U3 (7)
[0068] Since the zone 2 is shown as follows based on
V2+V3=U2+U1:
V2=U2+U1-V3=U2+U1-(U3+U1)=U2-U3 (8)
[0069] With respect to the other switching, a bumpless switching is
achievable by the same idea.
[0070] When a zone 2A, a zone 2B and a zone 2C in FIG. 1 are
respectively defined as the zones 1, 2 and 3, a switching
processing of a temperature control system for the three zones,
which is executed according to PID algorithm, will be described
below. A derivative term is omitted for simplification (PI
control).
[0071] Explanation of Codes
[0072] Codes in the following PID algorithm mean as follows. [0073]
MV1k_1, Kp_1, errk_1: a value of a proportional term, a
proportional gain, and an error of the zone 1; [0074] MV1k_2, Kp_2,
errk_2: a value of a proportional term, a proportional gain, and an
error of the zone 2; [0075] MV1k_3, Kp_3, errk_3: a value of a
proportional term, a proportional gain, and an error of the zone 3;
[0076] MV2k_1, MV3k_1, Ki_1: a value of a current integral term, a
value of a previous integral term, and an integral time of the zone
1; [0077] MV2k_2, MV3k_2, Ki_2: a value of a current integral term,
a value of a previous integral term, and an integral time of the
zone 2; [0078] MV2k_3, MV3k_3, Ki_3: a value of a current integral
term, a value of a previous integral term, and an integral time of
the zone 3; [0079] istop1, istop2, istop3: anti-windup commands of
the respective zones; [0080] buf: buffer (temporary escape); [0081]
MVfinal_1: a manipulated variable of the zone 1; [0082] MVfinal_2:
a manipulated variable of the zone 2; and [0083] MVfinal_3: a
manipulated variable of the zone 3.
[0084] <Algorithm>
% P Term Calculation
[0085] MV1k_1=Kp_1*errk_1;
MV1k_2=Kp_2*errk_2;
MV1k_3=Kp_3*errk_3;
% I Term Calculation
[0086] MV2k_1=MV3k_1+Kp_1*Ki_1*errk_1;
MV2k_2=MV3k_2+Kp_2*Ki_2*errk_2;
MV2k_3=MV3k_3+Kp_3*Ki_3*errk_3;
% Anti-Wind Up
[0087] if(istop_1==1)
[0087] MV2k_1=MV3k_1; [0088] end [0089] if(istop_2==1)
[0089] MV2k_2=MV3k_2; [0090] end [0091] % Manipulated variable
output for master-slave switching/cancellation processing if(the
master-slave relationship of the zone 3 is cancelled)
[0091] MV2k_1=MV3k_1+MV3k_3;
MV2k_2=MV3k_2+MV3k_3;
MV2k_3=MV3k_3;
MVfinal_1=MV2k_1;
MVfinal_2=MV2k_2;
MVfinal_3=MV2k_3; [0092] if(the master-slave relationship of the
zone 1 is cancelled)
[0092] MV2k_1=MV3k_1;
MV2k_2=MV3k_2+MV3k_1;
MV2k_3=MV3k_3+MV3k_1;
MVfinal_1=MV2k_1;
MVfinal_2=MV2k_2;
MVfinal_3=MV2k_3; [0093] else if(the cancelled state is switched to
set the zone 3 as the master)
[0093] MV2k_1=MV3k_1-MV3k_3;
MV2k_2=MV3k_2-MV3k_3; MV2k_3=MV3k_3;
MVfinal_1=MV2k_1;
MVfinal_2=MV2k_2;
MVfinal_3=MV2k_3; [0094] else if(the cancelled state is shifted to
set the zone 1 as the master)
[0094] MV2k_3=MV3k_3-MV3k_1;
MV2k_2=MV3k_2-MV3k_1;
MV2k_1=MV3k_1;
MVfinal_1=MV2k_1;
MVfinal_2=MV2k_2;
MVfinal_3=MV2k_3; [0095] else if(the zone 1 is set as the master in
place of the zone 3)
[0095] buf=MV3k_1;
MV2k_1=MV3k_1+MV3k_3;
MV2k_2=MV3k_2-buf;
MV2k_3=-buf;
MVfinal_1=MV2k_1;
MVfinal_2=MV2k_2;
MVfinal_3=MV2k_3; [0096] else if(the zone 3 is set as the master in
place of the zone 1)
[0096] buf=MV3k_3;
MV2k_3=MV3k_3+MV3k_1;
MV2k_2=MV3k_2-buf;
MV2k_1=-buf;
MVfinal_1=MV2k_1;
MVfinal_2=MV2k_2;
MVfinal_3=MV2k_3; [0097] else (when there is no switching)
[0097] MVfinal.sub..ltoreq.1=MV1k_1+MV2k_1;
MVfinal_2=MV1k_2+MV2k_2;
MVfinal_3=MV1k_3+MV2k_3; [0098] end
3. Operations in Embodiment(s)
[0099] Next, a specific process of the first exemplary embodiment
will be described with reference to a flow chart shown in FIG. 5.
In the following description, the zone 3 is defined as the master
loop ML.
[0100] Firstly, the supervisor 37 checks the temperature setpoint
of the setpoint setting section 35 of the zone 2B and the
temperature setpoint of the setpoint setting section 36 of the zone
2A (Step S1) and judges whether the temperature setpoints are
changed or not (Step S2).
[0101] When the temperature setpoints are unchanged, the supervisor
37 maintains the previous state (Step S11).
[0102] When the temperature setpoints are changed, the supervisor
37 checks the changed temperature setpoints (Step S3).
[0103] Next, the supervisor 37 checks the changing pattern of each
of the temperature setpoints (Step S4).
[0104] When the changing pattern of the temperature setpoints of
the zones is such that uniform temperature setpoints are changed to
uniform temperature setpoints, the supervisor 37 maintains the
setting of the zone 3 as the master loop without changing the
setting (Step S5).
[0105] When the changing pattern of the temperature setpoints of
the zones is such that uniform temperature setpoints are changed to
gradient temperature setpoints or gradient temperature setpoints
are changed to uniform temperature setpoints, the supervisor 37
determines whether to perform a heating control or a cooling
control (Step S6).
[0106] In the heating control, the supervisor 37 sets the zone
having the lowest temperature setpoint as the master loop ML (Step
S7). On the other hand, in the cooling control, the supervisor 37
sets the zone having the highest temperature setpoint as the master
loop ML (Step S8).
[0107] When the changing pattern of the temperature setpoints of
the zones is such that a first gradient pattern of temperature
setpoints is changed to a second gradient pattern of temperature
setpoints, the supervisor 37 determines whether the first gradient
pattern is inverted to provide the second gradient pattern (Step
S9).
[0108] When the first gradient pattern is inverted, the supervisor
37 cancels the setting of the master-slave relationship (Step
S10).
[0109] On the other hand, when the first gradient pattern is
non-inverted, the supervisor 37 maintains the previous state (Step
S11).
[0110] When finishing the above determination and setting the
master-slave relationship, the supervisor 37 outputs a command
according to the setting to the control processor 32 (Step
S12).
[0111] Subsequently, the supervisor 37 outputs a command of
switching the transformation matrix to the manipulated variable
converter 33 (Step S13).
[0112] Lastly, the supervisor 37 calculates the internal
temperature setpoints for the respective zones and outputs the
internal temperature setpoints to the error calculator 31 and the
control processors 32M, 32S (Step S14).
[0113] The error calculator 31 of each of the zones calculates an
error based on the internal temperature setpoint outputted from the
supervisor 37 (Step S15). The control processor 32 calculates the P
term, I term and D term in the PID control (Step S16).
[0114] The control processor 32 of each of the zones executes the
switching or cancellation processing between the master loop and
the slave loop based on the command outputted from the supervisor
37 (Step S17).
[0115] The control processor 32 of each of the zones calculates the
manipulated variable to output to the manipulated variable
converter 33 (Step S18).
[0116] The manipulated variable converter 33 switches the
transformation matrix based on the command of switching the
transformation matrix outputted from the supervisor 37 (Step
S19).
4. Check of Effects of Invention by Simulation
4-1. Structure of Control System in Simulation
[0117] The master-slave control of a three-input three-output
system will be exemplarily described with a simulation result
obtained by modeling a control system shown in FIG. 6. This control
system is a system for controlling a temperature of an aluminum
plate of 400.times.150.times.t4 as shown in FIG. 7 and uses an
actuator in a form of three thermo-modules configured to heat and
cool the plate. The temperature of the aluminum plate is measured
by three type K thermocouples provided near the respective modules.
The thermo-module and the thermocouples are intentionally disposed
asymmetrically relative to a longitudinal direction of the plate,
which is shown in dimensional detail in FIG. 7. Zones 1, 2 and 3
are defined from the left in the figure. Dynamic characteristics of
each of the zones are shown in Table 1. For a simple description,
the gain for the cooling control is defined as 1/3 as the gain for
the heating control while the time constant and the dead time in
the cooling control are the same as those in the heating
control.
TABLE-US-00001 Table 1 Heating Cooling Output Output Input 1 2 3
Input 1 2 3 zone 1 zone 1 K: gain 38.6 17.0 8.9 K: gain 15.9 6.5
3.1 T: time constant 102 214 321 T: time constant 98 171 236 L:
dead time 2 31 100 L: dead time 2 34 109 zone 2 zone 2 K 18.4 29.2
12.9 K 5.9 10.4 3.2 T 192 101 244 T 138 89 170 L 9 2 42 L 11 2 47
zone 3 zone 3 K 6.3 11.7 31.4 K 1.7 4.1 13.1 T 318 239 119 T 215
182 105 L 110 47 2 L 121 50 2
4-2. Problems in Typical Master-Slave Control
[0118] A controller capable of realizing a typical master-slave
control sets a control loop having the slowest response as the
master loop ML while setting the other control loop(s) as the slave
loop SL and controls the slave loop SL to follow the master loop,
as shown in FIG. 8.
[0119] This is because the control loop having the slowest response
cannot follow the other control loop(s) when all the temperature
setpoints are set uniform.
[0120] In heating and cooling by a plate with use of the above
control, the temperature of the plate is not always uniform, but,
depending on a usage, the temperature setpoints of the respective
zones are sometimes made different to give the plate a temperature
gradient.
[0121] In this configuration, it is only necessary to provide a
suitable offset temperature to the setpoint of the slave loop.
However, when a fixed master loop ML is used as in a typical
master-slave control, the following problems are caused.
[0122] First Problem
[0123] FIG. 9A shows results of the setpoint response by simulation
when the temperature setpoints of the respective zones are set
starting from 0 degree C. to:
(SV1, SV2, SV3)=(10.degree. C., 20.degree. C., 30.degree. C.).
[0124] FIG. 9B shows results of the setpoint response by simulation
when the temperature setpoints of the respective zones are set
starting from 30 degrees C. to:
(SV1, SV2, SV3)=(30.degree. C., 20.degree. C., 10.degree. C.).
[0125] In both of the above responses, the zone 1 demonstrates an
inverse response at the start of the heating (cooling), which
causes a dead time for a rise time. This is because the zone having
the highest (lowest) temperature setpoint is set as the master loop
ML in heating (cooling). For instance, when the master loop ML
starts being executed for heating, the slave loop SL is affected to
be temporarily executed for cooling against the master loop ML,
since the slave loop SL is supposed to offset the master loop ML.
Since the master loop ML usually demonstrates a slower response
than the slave loop SL, such a phenomenon becomes further
noticeable.
[0126] Second Problem
[0127] FIG. 10 demonstrates a response occurring when the
temperature setpoints of the respective zones are in a steady state
at (SV1, SV2, SV3)=(30.degree. C., 20.degree. C., 10.degree. C.),
switched to (SV1, SV2, SV3)=(10.degree. C., 20.degree. C.,
30.degree. C.) after the elapse of 1000 seconds, and further
switched to (SV1, SV2, SV3)=(30.degree. C., 20.degree. C.,
10.degree. C.) after the elapse of 2000 seconds.
[0128] The master loop ML is the zone 3. Although the temperature
setpoint of the zone 2 is constantly 20 degrees C., a large
fluctuation of the temperature setpoint occurs every time to switch
the temperature setpoints.
[0129] This is attributed to a temperature setting process of the
master and slave loops. As described above, in the temperature
setpoint setting for the master and slave loops, the master loop is
set at its own temperature setpoint but the slave loop is set at an
offset value against the master loop.
[0130] For instance, when the master loop ML is the zone 3 and the
temperature setpoints of the respective zones are set at (SV1, SV2,
SV3)=(30.degree. C., 20.degree. C., 10.degree. C.), the internal
temperature setpoint of the zone 3 as the master loop is 10.degree.
C., but the internal temperature setpoint of the zone 2 as the
slave loop is +10.degree. C. since an offset value against the
internal temperature setpoint of the zone 3 becomes +10.degree. C.,
and similarly the internal temperature setpoint of the zone 1 is
+20.degree. C. since an offset value against the internal
temperature setpoint of the zone 3 becomes +20.degree. C.
[0131] At this time, when the temperature setpoints are switched to
(SV1, SV2, SV3)=(10.degree. C., 20.degree. C., 30.degree. C.), the
internal temperature setpoint of the zone 3 is 30.degree. C.
Considering in the same way as described above, the internal
temperature setpoint of the zone 2 becomes -10.degree. C. and the
internal temperature setpoint of the zone 1 becomes -20.degree.
C.
[0132] Accordingly, the internal temperature setpoint of the zone 2
is switched from +10.degree. C. to -10.degree. C. although the
temperature setpoint of the zone 2 remains 20.degree. C. before and
after switching the temperature setpoints. In other words, at the
moment of switching the temperature setpoints, an error of
+10-(-10)=20.degree. C. occurs to affect a controlled target as the
manipulated variable.
[0133] As described above, in a typical master-slave control, the
above problems are caused by fixing the master loop and the slave
loop, resulting in deterioration of throughput in an actual
process.
[0134] In order to solve the first problem, the zone having the
lowest temperature setpoint is determined as the master loop ML in
the heating control, while the zone having the highest temperature
setpoint is determined as the master loop ML in the cooling
control.
[0135] For instance, in the examples described in FIGS. 9A and 9B,
the zone 1 having the lowest temperature setpoint is set as the
master loop ML in the heating control shown in FIG. 9A, while the
zone 1 having the highest temperature setpoint is set as the master
loop ML in the cooling control shown in FIG. 9B.
[0136] With this setting, the zone 1 is heated in a manner to boost
heating of the zones 2 and 3 in the heating control, while the zone
1 is cooled in a manner to boost cooling of the zones 2 and 3 in
the cooling control.
[0137] In other words, since the responses of all the zones are
directed in the same direction, more stable responses can be
obtained.
[0138] FIGS. 11A and 11B show results obtained when the zone 1 is
set as the master loop ML under the same conditions as in FIGS. 9A
and 9B. It is recognized that the results show more stable
responses than those obtained when the zone 3 is set as the master
loop ML.
[0139] A solution of the second problem is to cancel the
master-slave relationship when the gradient temperature setting is
changed to an inverse gradient temperature setting.
[0140] By cancelling the master-slave relationship, the temperature
setpoint coincides with the temperature setpoint to reduce a
drastic change in the error generated when inverting the gradient
temperature, so that an influence on the response is decreased.
[0141] FIGS. 9A and 9B show results obtained when the master-slave
relationship is cancelled under the same conditions as in FIG. 10.
It is recognized that overshoot and undershoot of the zone 2 are
significantly reduced.
[0142] Since an inverse response and a fluctuated response in the
setpoint response are reduced by the aforementioned process as
described above, it was confirmed by simulation that throughput is
improved in an actual process.
* * * * *